In a printer, based on the printing data fed from an upward unit, the line is printed one after another by shifting the print head along the form in a specific direction and, when a specific line has been printed, after the form is shifted in the direction intersecting at a right angle with the specific direction for feeding lines, a next line is printed. When this line feed is made, the traveling distance, that is, amount of the line feed of the form is properly set, and two continuous lines are overprinted so that at least their part is overlapped, or a blank area is left between adjacent lines.
Among such conventional printers, there is one in which a pressure is applied to the form to print to a desired depth of color. Such printers are described in, for example, U.S. Pat. No. 5,048,984.
Incidentally, in this type of printer, when the amount of line feed is made small for overprinting, since the pressure is applied to the same area of the form plural times, if the printing density is especially high, wrinkle or breakage is caused to the form due to this repeatedly applied pressure.